Horizontal and vertical measurements are essential operations for construction of indoor and outdoor structures in building and civil engineering works and for installation of machines and the like. For these measurement operations, relatively simple devices such as weighted suspension devices, spirit levels and water-containing rubber tube levels and optical measurement instruments have been usually employed.
However, for simple measurement, when the weighted suspension string is employed, it has been followed that first of all, one worker stands in a predetermined position holding the weighted string or positions an upper portion of the string along a wall on which a line is to be marked and another worker marks a point of perpendicularity on the wall while restraining the weight against swinging and thereafter, they mark a vertical line on the wall between the predetermined position or the fixed upper portion of the string positioned and the point of perpendicularity using an ink pad and a ruler, that is, the conventional vertical measurement requires two separate operation steps. Further, also when a horizontal line is to be marked on a wall, it is necessary that two spaced points are set on the wall in alignment with each other in a horizontal plane and a line is marked connecting between the two points.
Thus, also when horizontal and vertical lines are to be marked on objects having different heights and widths by the conventional methods, workers have to perform line marking operations while repeatedly ascending and descending foot stools and/or ladders resulting in loss of labor and time.
Also when a line is marked on a wall panel employing a carpenter's ink pad assembly including an ink pad, a pointed leader, a length of rolled string extending between and secured at the opposite ends to the pad and leader and a handle for hauling the string in, the leader is anchored to the wall panel at a selected point on the panel, the string is unrolled and tensed and the tensed string is caused to strike against the panel. One example of the carpenter's ink pad assemblies is shown in Japanese Laid-Open Utility Model No. 170796/1977. Although the entire line marking operation can be performed by a single worker, when an object on which a line is to be marked is formed of hard material such as concrete or steel, the line marking employing the ink pad assembly still has the drawback that two workers are required to perform the operation, that is, one worker assigned to manipulate the leader and another worker assigned to manipulate the ink pad.